Hobart 90 C 20 Operation And Maintenance Manual page 93

main on when the switch is released and allowed to return to the center ON position. This indicates
that the load contactor is closed and the plug interlock relay is functioning properly.
(23) Apply 1/3 to 1/2 load at the load bank and allow the unit to run for 15 to 30 minutes. Observe op-
eration of all monitoring instruments.
(24) Increase load bank resistance to apply a full load.
(25) Check operation of the governor by observing the frequency meter (1, Fig. 1) when generator is
switched from no-load to full-load and vice versa. Use the contactor control switch (20) to apply and
remove load several times. Frequency drop should be no more than 1 Hz. Adjust governor if neces-
sary (see Para. 4, E, (3)).
(26) Follow instructions in Para. 4, B, (2) (b) to set voltage regulator line drop compensation potenti-
ometers. Set knob pointer on cable size potentiometer to size (2/0, 4/0, etc.) of cable being used. Set
knob pointer on cable length potentiometer to length (20 feet, 40 feet, etc.) of cable being used. See
instruction plate (mounted below knobs).
(27) Check voltage regulator, at intervals, from no-load to full load, and on up to 125% load. Observe
and note voltage at various loads. Voltages should vary no more than plus or minus 1% from 115 V.
(28) Check accuracy of voltmeter.
(a) Open generator control tray (14, Fig. 1).
(b) Connect a master voltmeter of known accuracy to terminals of the voltmeter (2).
(c) Compare unit voltmeter reading with master meter. Error must not exceed 2% of full scale.
(29) Check accuracy of AC ammeter.
(a) Connect a master ammeter of known accuracy to the AC ammeter (4) terminals.
(b) Compare unit ammeter reading with master meter under various loads. Error must not exceed
4% of full scale.
(30) Check operation of meter selector switch (5). A voltage value should be shown in each switch po-
sition.
(31) Check operation of the line switch (6). A normal voltage of 115 V AC should be indicated when
the switch is in LINE-TO-NEUTRAL position. A voltage of approximately 200 V AC should be indi-
cated when the switch is placed in LINE-TO-LINE position.
(32) Check accuracy of frequency meter.
(a) Connect a master frequency meter of known accuracy to the frequency meter (1) terminals.
(b) Compare meter readings. Error must not exceed 1% of full scale.
(33) Operate the unit not less than 10 minutes under full load. The overload device (Ref. 1-1; 7, Fig.
11) MUST NOT trip.
(34) Operate at 125% rated load for 5 minutes immediately following the full load run. The overload
device MUST trip within 5 minutes and the overload indicating light (9, Fig. 1) must come ON to indi-
cate an overload condition.
(35) Reduce load to normal. Turn off indicating light by pressing reset switch (7, Fig. 1).
August 5/89 Revised
OM-2031
2-3
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